872 THE GEOLOGY OF THE NANDEVVAR MOUNTAINS, 



on a line which runs S.W. from the Nandewars to the Warrum- 

 bungles, thence S.S.W. to Dubbo and Minore, thence S.E. to the 

 Canoblas, and continues in the same direction to Mittagong, 

 with outlying extrusions of a dark green variety as far west as 

 Goulburn. It is likely that other alkaline trachytes and allied 

 lavas will be met with between Barrigan and the Nandewars, 

 and between Barrigan and Mittagong. If so, the belt of alkaline 

 lavas forms a loop round the Gunned ah basin of Upper Coal 

 Measure strata. The significance of this matter I propose to 

 discuss more fully in a later paper. 



It is also interesting to note that some considerable masses of 

 fine limonite, iron ore, occur on Doyle's farm near Gibraltar close 

 to Dubbo. On the Coonabarabran-Cobborah road, not far from 

 Mundooran, some of the sandstones are so indurated with iron, 

 in the form of haematite, that they could be smelted for iron. I 

 have already mentioned that valuable deposits of a similar nature 

 occur round the Warrumbungle Mountains. There is no doubt 

 that in time all these districts will be worked for iron. 



The origin or source of the iron I have not investigated, but 

 as it occurs most frequently in the vicinity of igneous rocks it 

 may have been derived from them by leaching, like the iron ores 

 similarly situated near Mittagong.* 



B. Petrology. 



The rocks of the Nandewar Mountains may be divided into 

 A. The Volcanic Series, consisting of : — 



(a) Ali-rhyolites (alkaline rhyolites), including comendite 

 and quartz pantellarite. 



(b) Ali-trachytes (alkaline trachytes), including soda- 

 trachyte, pantellarite, <fec. 



/ (c) Phonolites. 

 I (d) Alkaline andesites. 

 I (e) Alkaline basalts, 

 (f) Calcic rhyolites and basalts. 



* Taylor, T. Griffith, and Mawson, D., 'The Geology of Mittagong,' 

 Journ. Proc. Roy. Soc. New South Wales, Vol. xxxvii. 



